Caliper system for signature machines

ABSTRACT

A CALIPER SYSTEM FOR A CYCLICALLY OPERABLE SIGNATURE GATHERING MACHINE IN WHICH EACH UNBOND BOOK OF SIGNATURES MOVING TOWARD A BINDING STATION PASSES BETWEEN A FIXED SUPPORT AND A MOVABLE ROLLER PROBE THAT IS BIASED TOWARD THE SUPPORT SO THAT THE PROBE POSITION IS A FUNCTION OF BOOK THICKNESS. THE PROBE IS CONNECTED TO THE MOVABLE ELEMENT OF A LINEAR VOLTAGE DIFFERENTIAL TRANSFORMER OR OTHER ELECTRICAL TRANSDUCER, DEVELOPING A BOOK THICKNESS SIGNAL OF GIVEN FREQUENCY AND AMPLITUDE. THE BOOK THICKNESS SIGNAL IS COMPARED WITH A REFERENCE SIGNAL OF CORRESPONDING FREQUENCY HAVING AN AMPLITUDE REPRESENTATIVE OF A CORRECT BOOK THICKNESS TO CONTROL MACHINE OPERATION AND PREVENT BINDING OF INCORRECTLY ASSEMBLED BOOKS.

May 23, 1972 W. B. MCCAIN ET AL 3,664,655

CALIPER SYSTEM FOR SIGNATURE MACHINES Filed SCpt. 25, 1970 4 Sheets-Sheet l wI-Hlm 5- McCal'n, dames F. Cosgrove BzfM/3w,1 orn nucl Zic/kaal:

H'Hzorn ms May 23, 1972 W. B. Mmm ET AL 3,664,666

CALIPER SYSTEM FOR SIGNATURE MACHINES 4 Sheets-Sheet 2 Filed Sept. 25, 1970 g Vo Ve Alf/auf l Invenors william. B. McCain. James F. Cos

May 23, 1972 Filed Sept. 25, 1970 REFERENCE STATION W. B. MCCAIN ET AL CALIPER SYSTEM FOR SIGNATURE MACHINES 4 Sheets-Sheet 3 CALIPER STATION CS W 4o L l MACHINE POWER Co N-mol. 'COM PA RATOR SU P P LY Tl 68 2 if 67 40 MACHINE Powrz-,R CONTROL COMPARAToR e SUP P LY REF-'E RENCE STATI.

l j CAMPER STM-lon CS Inventors 'William B. McCain. James F. Cosgrove Y' Morne/f8 May 23, 1972 W. B. MsC/MN ET AL 3,664,655

CALIPER SYSTEM FOR SIGNATURE MACHINES 4 Sheets-Sheet 4 Filed Sept. 25, 1970 mm3 @wmfy v .C ,mn m wrm 'I .lull .I'II

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S DIMM ad 'Zit/kuni United States Patent Office 3,664,655 Patented May 23, 1972 Int. Cl. B65h 43/02 U.S. Cl. 270-56 13 Claims ABSTRACT F THE DISCLOSURE A caliper system for a cyclically operable signature gathering machine in which each unbound book of signatures moving toward a binding station passes between a fixed support and a movable roller probe that is biased toward the support so that the probe position is a function of book thickness. The probe is connected .to the movable element of a linear voltage differential transformer or other electrical transducer, developing a book thickness signal of given frequency and amplitude. The book thickness signal is compared with a reference signal of corresponding frequency having an amplitude representative of a correct book thickness to control machine operation and prevent binding of incorrectly assembled books.

CROSS REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to signature machines for assembling books, magazines, .and other publications (referred to generically herein as books) from signatures juxtaposed one on another.

A book is usually assembled from a plurality of signatures. A signature is simply a folded sheet presenting four pages (two sheets) of the book. In the instance of small books, such as magazines, newspaper supplements, entertainment guides, catalogs of limited size Iand the like, the signatures to comprise the book are fed from supply hoppers and are gathered, one atop another, on a conveyor. The conveyor delivers each group of signatures, constituting an unbound book, to a stitching or other binding station. At the binding station, staples are driven through the backbones (the edge of the fold) of all of the signatures to complete a bound book, as one example of commercial application.

Staple stitching is one way of binding the signatures into a book. The staples clinch the backbone, and this is known as saddle stitching. On the other hand, the staples may be pressed through the back of the book along one side of the backbone, in what is known as side wire binding, resulting in a square-backed book. `Binding may also be effected with glue, a cover being glued to the backbones of the signatures, in what is known as perfect binding. The present invention is applicable to all of these different forms of binding.

It is ordinarily desirable to interrupt operation of the binding means in a signature gathering machine in the event the unbound book delivered to the binding station does not contain the required number of signatures. Salvage is one reason; the absence of a complete signature group or the presence of a surplus signature group represents another reason, because operation of the binder can foul the machine with fugitive staples, for example. Accordingly, it is customary to caliper each unbound book as it advances toward the binding station to determine if the book is too thick or too thin. Either departure from correct thickness requires interruption of the binding means.

Calipering is presently performed, in one practical mechanism, as a mechanical operation in which each book is gauged between a pair of rollers normally spaced from one another by a distance representing a book of correct thickness. One roller, in effect, fathoms the book thickness, sinking or rising, as it were, if the book is too thin or too thick. 4In response to either event a switch or other mechanical sensing device is actuated to register the occurrence of a bad book. Calipering naturally occurs ahead of binding, so that it is necessary to store caliper information concerning a bad book until that book arrives at the binding station. A signature machine embodying an effective mechanical caliper of this kind is disclosed in McCain Patent No. 3,191,925.

The mechanical caliper is eminently satisfactory in many applications. But the mechanical caliper may not be able to fulfill the requirements of some publishers. Certain publishers, for example, publish expanded regional or provincial issues of their magazines. Thus, regional magazines distributed in one part of the country may require a signature content different in some respects from those distributed elsewhere. There may be literally scores of different issues, entrailing considerable programming of the signature machine, but mechanical calipers are not ordinarily that flexible.

In the caliper system that is described and claimed in the aforementioned co-pending application Ser. No. 748,- 380, the thickness of each unbound book is measured by a beam of high energy particles that is directed through the book as a probe. For example, a beam of beta particles from a strontium source may be employed. The energy level of the probing beam, as it emerges from an unbound book, is sensed and is compared with a similar energy analog developed by a corresponding beam projected through a standard book of correct thickness. The comparison determines whether the unbook book matches the current requirements for the signature gathering machine. |If a match is determined, the unbound book is passed on to the binder. lf a mismatch, comprising an unbound book that is too thick or too thin, is detected, the unbound book is rejected.

The beam-probe caliper system is extremely accurate and permits great flexibility in the operation of the signature gathering machine. The caliper accuracy can be readily controlled to detect a variation in thickness of less than two sheets (one signature) without the necessity for expedients such as multiplying levers and the like required in mechanical Calipering apparatus. That same system makes it possible to change over, almost instantaneously from one selected standard book thickness to another, and extremely useful and valuable attribute, particularly in the assembly of different editions of nationally distributed magazines that require variations in the magazine content. Moreover, the system is readily adaptable to complete remote control.

On the other hand, the radiation projection and detection equipment required for the caliper system of application Ser. No. 748,380 can be relatively expensive and is often justied only for use in extremely high production signature gathering machines. Moreover, some potential users do not want to incorporate high energy radiation equipment in their plants, on the basis of a potential radiation hazard to production workers, despite the fact that the radiation probe equipment can be made quite safe and does not necessarily entail an undue industrial hazard. Thus, there exists a definite and continuing need for a Calipering system that affords at least most of the attributes and advantages of the aforesaid radiation probe system, but that is not dependent upon the use of a high energy radiation beam.

SUMMARY OF THE INVENTION 'It is a principal object of the present invention, therefore, to provide a new and improved electrical caliper system for a high speed cyclically operable signature gathering machine, of the kind in which signatures are gathered into unbound books and subsequently bound, which system atiords a rapid response to the detection of an unbound book of incorrect thickness and provides a high accuracy in the detection of unbound books of incorrect thickness, yet is not dependent upon the use of a high energy probing beam or other apparatus utilizing hard radiations.

Another object of the invention is to provide a new and improved electrical caliper system for a signature gathering machine that is highly selective and flexible in operation, and is particularly suited to the assembly of magazines and other publications in lwhich dilering editions have minor differences in total content.

A further object of the invention is to provide a new and improved electrical caliper system for a signature gathering machine that inherently provides for effective remote control of the machine.

A specific object of the invention is to provide a new and improved electrical caliper system, having the attributes set forth immediately above, that is simple and inexpensive in construction and operation, yet highly reliable over long periods of operation.

Accordingly, the invention relates to a caliper system for a cyclically operable signature gathering machine of the kind in which signatures are gathered from a plurality of supply sources into individual unbound books each containing a given number signatures, and in which the unbound books are advanced seriatim along a predetermined path through a calipering station to a binding station at which the books are bound in their sequence of arrival, the machine including control means for controlling its operation. A caliper system constructed in accordance with the invention comprises reference means for developing an alternating current electrical analog signal having a given parameter representative of the correct thickness for an unbound book. That parameter usually constitutes the amplitude of the signal, but can comprise the frequency or even the phase of the signal. A lixed support is located on one side of the book path, and a probe element is mounted on the opposite side of the path, at the caliper station; the probe element is aligned with the fixed support and is movable toward and away from that support. Biasing means are provided, urging the probe element toward the lixed support so that, when an unbound book passes through the caliper station, it displaces the probe element from the lixed support by a distance equal to the thickness of the book. An electrical transducer which may be a linear voltage di'erential transformer, is connected to the probe element and is employed to develop an alternating current book thickness signal; the corresponding parameter of the book thickness signal varies in accordance with the actual thickness of the unbound book. Comparison means are provided for comparing the analog signal and the book thickness signal to determine whether a match or a mismatch prevails, and for developing a control signal indicative thereof. The control signal is supplied to the control means of the signature gathering machine to preclude binding of mismatched books.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a known machine in lwhich the present invention may be used;

FIG. 2 is a detail view showing features of signature gathering;

FIGS. 3, 4, 5 and 6 are Iviews showing a stitcher head and its controls to prevent wire feed;

4 FIG. 7 is a sectional view, partly diagrammatic, illustrating one form of the present invention;

FIGS. 8 and 9 are, respectively, views showing other embodiments of the invention, these views in part being both schematic and diagrammatic.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The signature machine illustrated in FIG. 1 comprises, at the right-hand side as viewed in this figure, a pair of signature supply hoppers H1 and H2 which are partly hidden from view by a pair of raised cover plates C1 and C2. Plates C1 and C2, when lowered, cover parts consituting means by which signatures are removed individually from each related hopper. The signatures S-1 and S-2, FIG. 2, are withdrawn from the hoppers and eventually deposited, in a spread state, on a saddle conveyor track SD located at the front of the machine below the supply hoppers. The gathering operation is fully disclosed in McCain Pat. No. 3,087,721; accordingly, only those features entailed in an understanding of Ithe basic machine functions are described here.

A signature S-1 from supply hopper H1 is first deposited on the saddle; this signature is then advanced along the saddle toward hopper H2 by a feed lug 20 carried by a conveyor chain 25 FIG. l. The second signature S-2 for the book is dropped, from hopper H2, on top of the first signature. As is evident in FIG. 2, signatures on the saddle are in a spread state with the folded backs (backbones) at the top of the saddle.

The foregoing describes generally parts that are located at the signature gathering station ofthe machine, identified generally at GS in FIG. l. A group of signatures thus gathered into booklet form are moved as a unitary body along the saddle, to the left as viewed in FIG. l, toward the signature stitching apparatus SR, FIG. 1, and are deposited by the aforesaid feed elements in a stationary state beneath a pair of stapling heads SH identifying the location of the stitching station. It is here -that staples or other fastening elements are passed through the backs of the signatures in each signature group to complete the formation of the book.

The books are formed seriatim and moves sequentially to the binding station where the stitching heads or other binding means are effective to join the signatures in each group to form a complete book. Several cycles of machine operation are entailed between the gathering of signatures into one complete group, the unbound book, and binding of the book at the binding station. In order to avoid stitching or binding of an incomplete group of signatures, each group of signatures is first calipered at a calipering station. The calipering operation precedes binding by at least one machine cycle. The calipersing station, for example, may be in the position CS, FIG. l.

Before describing in detail the caliper systems constituting the present invention, we shall first explain the net effect of determining that a book (unbound signature group) of incorrect thickness is approaching the binding or stitching station SR, FIG. l, such explanation being founded on the disclosure in McCain Pat. No. 3,191,925. In fact, FIGS. 3, 4 and 5 hereof correspond to FIGS. l2- 14 of Pat. No. 3,191,925; only reference characters have been changed.

Each stitching head SH, FIG. 1 incorporates a stitching wire control as illustrated in FIGS. 3, 4 and 5. The wire W, FIG. 4, for forming the staple is fed between a pivotal feed dog 30 and a cooperating anvil 31. When the wire is gripped between the two, FIG. 4, the Wire is fed downward incidental -to penetrating the group of signatures and clinching a staple thereto. This occurs upon downward movement of the bender bar 32. However, by pivoting the feed dog 30 to the open or released position shown in FIG. 5, wire feed for forming a staple is interrupted. This is accomplished by actuating a bell crank lever 35, pivoting the bell crank from its normal inactive position, FIG. 5,

where the lower end 36 thereof is effective on the upper end of the feed dog 30 to shift the latter to its released position. Suh action is timed to occur when an incorrect book arrives at the stitching station.

Movement of the bell crank 35 to interrupt or disable wire feed in the proper cycle of the machine occurs as an incident to energizing a solenoid, as can be readily visualized, and as explained in full detail in Pat. No. 3,191,925. Nonetheless, reference may be made to FIG. 6 hereof for a schematic representation of the actuating forces involved, established upon energization of control solenoid 40. Solenoid 40 is thus representative of one form of control means ultimately responsive to the generation of a control signal at the calipering station indicative of an incorrect book. The construction of the calipering system, and the means for generating an appropriate control signal, will now be described.

The caliper system illustrated in FIG. 7, constituting one embodiment of the present invention, is located at the caliper station CS of the machine (see FIG. 1). FIG. 7 shows an unbound book B positioned at the caliper station and ready for calipering. The book B has been advanced to the calipering station by the conveyor comprising chain 25 and feed lug 20, which move the books along the saddle track SD.

Caliper system 50 includes a reference means 51 for developing an alternating current electrical analog signal representative of the correct thickness for an unbound book. In the system 50, the reference means includes a correctly assembled unbound book B1, used as a standard, supported by appropriate means such as the plates 52 and 53. Plate 53 is provided with an aperture 54 that is aligned with a fixed reference support 55, preferably including a roller 56. The unbound book B1 is engaged on one side by the reference support roller 56 and is engaged on the opposite side by a probe roller 57. The probe roller 57 is mounted in a bracket 58 that is in turn aixed to a shaft 59 connected to the movable element of an electrical transducer 60.

The transducer 60 may comprise one of a number of different mechanical-electrical transducer devices. For eX- ample, the transducer 60 may comprise a transformer including at least an input winding and an output winding together with a movable core for varying the coupling ratio between the transformer windings. With a transducer of this kind, the movable core is mechanically connected to the probe element comprising members 57-59. More specifically, the transducer 60 may constitute a linear voltage differential transformer having its movable element connected to the probe roller 57 by means of the bracket S and the shaft 59.

In an adjustable transformer, used for the transducer 60, the output of the transducer comprises a control signal that varies in amplitude in the accordance with the `thickness of the standard book B1. However, other signal parameters can be varied, in accordance with the standard book thickness, instead of the signal amplitude. Thus, the transducer 60 may comprise a variable oscillator having an adjustable impedance or other adjustment member connected to the probe roller 57 by the bracket 58 and the shaft 59. With a transducer of this kind, it is the frequency of the control signal that is adjusted in accordance with the thickness of the standard book B1 instead of the amplitude. With either kind of transducer, however, the reference means 51 generates an alternating current electrical analog signal that has a given parameter (amplitude, frequency, or phase) that is representative of the correct thickness for a book, determined by the thickness of the standard book B1.

The caliper station CS includes sensing apparatus that is essentially similar to the equipment described above for the reference means 51. Thus, one of the saddle plates SD is provided with an aperture 70. A xed support 61 is aligned with the aperture 70; the xed support includes a roller 62 that projects through the aperture 6 70 and engages one side of the unbound book B as the book B traverses the caliper station.

A probe element is mounted at caliper station CS on the opposite side of the book path from the iixed support 61, 62. The probe element comprises a probe roller 63 mounted in a bracket 64 that is affixed to a shaft 65. The shaft 65 is movable, in an axial direction, toward and away from the fixed support roller 62. The shaft 65 is connected to the movable element of an electrical transducer 66, which may comprise a linear voltage differential transformer. The transducer 66 includes internal biasing means urging the shaft 65 outwardly of the transformer 66 and hence urging the probe element comprising the bracket 64 and the roller 63 toward the xed support 61, 62. The transducer 66 may take other forms, as in the case of the previously described transducer 60 at the reference station. The transducers 60 and 66 are matched in their characteristics and both are energized from the same power supply 67.

The output of each of the two transducers 60 and 66 is applied to a comparator 68. In those systems in which the transducers 60 and 66 comprise linear voltage differential transformers or other adjustable transformers, the comparator 68 constitutes an amplitude comparison circuit. If the transducers 60 and 66 are constructed as variable-frequency oscillators, the comparator 68 is a frequency discriminator. If variable-phase transducers are employed, a phase discriminator may be employed for the comparator 68. Inasmuch as a variety of elfective comparator devices for amplitude, phase, and frequency are well-known in the art, specific operating circuits for the comparator have not been illustrated.

The output of the comparator 68 is connected to the input of a machine control circuit 71. The machine control circuit 71 is representative of the control means for the signature gathering machine, and includes the binding control solenoid 40.

As can be seen from FIG. 7, the position of the probe roller 63, during the time interval in which an unbound book B traverses the caliper station CS, is determined by the thickness of the unbound book B. The position of the probe 63 in turn, determines the displacement of the shaft 65 inwardly of the transducer 66, and thus determines the instantaneous setting of the transducer. Accordingly, the transducer 66 develops an alternating current book thickness signal having an amplitude (or other parameter) which varies in accordance with the actual thickness of the moving unbound book B. As indicated above, the variable parameter for transducer 66 is the same as for transducer 60, matched transducers of similar construction being employed.

Consequently, the comparison of the two signals from the transducers 60 and 66 that is carried out in the comparator 68 determines Whether the standard book B1 is matched in thickness by the unbound book B. If the two books are matched in thickness, the control signal output from the comparator 68 is such that the machine control 71 leaves the solenoid 40 de-energized, permitting binding of the book B when it reaches the binding station in the machine. On the other hand, if a mismatch is determined, indicating that the book B is significantly thicker or thinner than the standard book B1, the machine control 71 is actuated to reject the unbound book and preclude operation of the binding apparatus by energizing the solenoid 40. The machine control 71 is also effective to transfer the unbound mismatched book B to an alternate output location for the machine to avoid mixing good bound books with bad unbound books, as described more fully hereinafter in connection with FIG. 9.

FIG. 8 illustrates the application of the system of FIG. 7 to a signature gathering machine employed for side wire binding or for perfect binding instead of saddle binding. The components of the system remain essentially unchanged but they are oriented differently to accommodate the different orientation of the unbound books as they move in at condition along a horizontally disposed support SS. Thus, each unbound book B moving through the caliper station CS is disposed horizontally. The book B engages a fixed support comprising a bracket 61 and a roller 62 located at one side of the path of movement for the books. A probe comprising a roller 63 mounted in a bracket 64 is located at the opposite side of the path, in alignment with the xed support roller 62. The spacing of the probe roller 63 from the support roller 62 is determined by the thickness of the book B and, in turn, determines the vertical position of a shaft 65 that is connected to the adjustable element of an electrical transducer 66.

The reference means 51', in the apparatus of FIG. 8, is essentially a duplicate of the calipering equipment located at the caliper station CS. A standard correct book B1, located upon a stationary plate 73, engages a lixed support comprising a roller 56 mounted in a bracket 55. The opposite side of the book B1 is engaged by a probe roller 57 mounted in a bracket 58 that is connected to the shaft 59 of an electrical transducer 60. As before, the transducers 60 and 66 are of the same type and are matched in their characteristics; each produces an alternating current electrical signal representative of book thickness. The signal from the transducer 60 is an analog of the correct thickness for an unbound book, as represented by the standard book B1. The output signal from the transducer 66 is an alternating current book thickness signal corresponding to the actual thickness of the unbound book B. The analog signal and the book thickness signal are compared in a comparator 68, producing a control signal that is supplied to the machine control 71. As before, the control signal is utilized to inhibit binding of mismatched books by controlling the energization of the binding solenoid 40.

FIG. 9 shows an overall control system for a signature gathering machine that is presented to illustrate more completely the operating interrelationship between the caliper system and the machine. In the machine, as illustrated in FIG. 9, there are four signature hoppers H1 through H4 positioned at the left-hand side of the machine. A conveyor 25 driven by a conveyor drive 81 extends through most of the machine. The signature groups or books deposited on the conveyor are advanced through the machine from left to right in FIG. 9 as indicated by the arrow A. In the right-hand portion of the machine, the conveyor belt 25 terminates in a transfer station 82. Books reaching the transfer station 82 can be directed along a main continuation conveyor 25' through a binder station SR to a destination at which usable books are collected. Alternatively, the transfer station 82 may be operated to divert mismatched books along a conveyor chain 25" to a destination for reject books.

The caliper system 90 illustrated in FIG. 9 may correspond to either of the specific systems described above in connection with FIGS. 7 and 8. The caliper system 90 includes three separate reference stations 91, 92 and 93 each capable of developing an alternating current electrical analog signal for an unbound book of a given thickness. By Way of example, the device 91 may develop an analog signal for a book having a thickness corresponding to the total thickness of two signatures S1 and S2. The analog device 92 may develop an analog signal for an unbound book having a thickness equal to that of the three signatures S1, S2 and S3. The analog reference device 93 may afford an analog signal corresponding to the overall thickness of four signatures S1-S4, one from each of the hoppers H1-H4. The analog reference devices 91-93 may each utilize any appropriate form of transducer as discussed above.

The outputs of the three analog reference devices 91, 92 and 93 are connected to a book selector 94, which may comprise a simple three-position selector switch. The book selector circuit 94 is connected to one input of a comparator 68. The book selector 94 is also connected to a hopper control device 95 that determines which of the hoppers H1 through H4 are actuated in the compiling of any given series of books.

The caliper system of FIG. 9, like those described above, includes a fixed support comprising a bracket 61 and a roller 62, engaged by each of the unbound books traversing the caliper station CS. A probe roller 63 is located on the opposite side of the path of the books from the roller 62. As before, the probe roller 63 is mounted in a bracket 64 aixed to the movable element shaft 65 of a mechanical-electrical transducer 66. The output of the transducer 66 is an alternating current book thickness signal having an amplitude (or other parameter) that varies in accordance with the position of the roller 63 and hence in accordance with the thickness of an unbound book moving through the caliper station CS.

The output of the comparator 68, in the embodiment of FIG. 9, is connected to a comparator gate circuit 1011. The comparator gate circuit 101 has a second input that is coupled to the conveyor drive 81 so that the comparator gate may be actuated once in each cycle of machine operation. That is, the comparator gate 101 is actuated to an open condition for a given time interval each time one of the unbound books advances a full stage along the path between the signature hoppers and the output end of the machine.

The output of the comparator gate 101 is connected to the input level of a multi-level storage register 102. The register 102 may be a conventional shift register and has a shift input derived from the conveyor drive 81 so that the data stored in the register 102 is advanced one level in each cycle of machine operation. One of the intermediate stages of the storage register 102 is coupled to a transfer control circuit 103 that actuates the transfer station 82. A later stage in the storage register, which may be the terminal stage of the register, is connected to a binder control circuit 104. The binder control circuit, `which may include the binding means control solenoid 40 described above, is connected to and actuates the binding means SH.

In considering the operation of the system illustrated in FIG. 9, it may be assumed that the book selector 94 is set initially for books containing only signatures S1 and S2 from hoppers H1 and H2. The book selector 94 conditions the hopper control 95 so that a signature from each of the hoppers H1 and H2 is deposited upon the conveyor represented by the chain 25 in each cycle of machine operation. The hopper control also functions to prevent discharge of any of the signatures from hoppers H3 and H4.

As each unbound book reaches the caliper station CS, the thickness of the book is sensed by the probe means 63, -64 and the associated transducer 66. The output of the transducer 66 is compared in circuit 68 with the signal from the electrical analog device 91 that has been selected by the selector circuit 94. The output of the comparator' is supplied through the comparator gate 101 to the initial stage of the storage register 102 and is recorded therein for subsequent use.

In each continuing cycle of machine operation, the information as to -match or mismatch that was initially stored in the first level of the register 102 is advanced through the storage register in synchronism with the operation of the conveyor drive 81 of the machine. Three cycles later, for the machine as illustrated, the stored information actuates the transfer control 103 to direct the book along the main output conveyor 25 if the stored information indicates that the book matches the requirements of the system.. On the other hand, if the stored information indicates a mismatch, the book is diverted along the auxiliary conveyor represented by the chain 25". Two cycles later, the stored information in the register 102 is supplied to the binder control 104 to inhibit or to permit operation of the binder means SH, depending upon whether a mismatch or a match situation was determined at the caliper station.

As operation of the machine continues, the book selector 94 can be actuated to select a different combination of signatures. The operation proceeds as above except that the hopper control 95 actuates the required different combination of hoppers and the calipering operation is carried out on the basis of the different thickness requirements determined by the new signature combination. It is thus seen that the caliper system 90 is completely integrated with the overall machine operation and accords maximum flexibility of control for the machine.

It will be apparent that a number of variations can be made in the internal connections of the control system of the system of FIG. 9 without departing in any way from the basic control operation. For example, the hopper control 95 is shown as having a mechanical connection to the conveyor for synchronization of the hopper operations with the conveyor movement, but electrical synchronization may be employed if desired. The output of the comparator'68 is synchronized with machine operations by the connection through the comparator gate 101, but the same effect can be achieved by appropriate gating of the inputs to the comparator to protect against erroneous sensing when the space on the conveyor between adjacent books is being scanned by the caliper system. The storage register 102 is a preferred means for synchronization of the transfer station and binder operations with the functioning of the caliper system 90, but separate delay circuits for these two functions could be utilized. The transfer station 82 can be located after the binder station SH if desired, with appropriate re-connection of the transfer and binder controls to different levels in the storage register 102. However, none of these modifications affects the basic functioning of the system.

From the foregoing description of various embodiments of the invention, it can be seen that the unbound books are calipered by sensitive electrical equipment which effectively avoids the inherent inertia of a mechanical caliper. The biasing means employed to maintain the probe element, such as the roller 63, in engagement with each unbound book can be relatively weak; in some instances, as in the arrangement of FIG. 8, gravity alone may be utilized. With appropriate mechanical-electrical transducers, a high-degree of sensitivity can be readily achieved, permitting error detection response in terms of a singlepage departure from a book of correct thickness. At the same time, the invention contributes substantially to the versatility and flexibility of operation of the signature gathering machine, since the standard book thickness can be changed for any of the analog signal generators 91-93 simply by inserting a different standard book therein. Moreover, a Iplurality of standards can be utilized for a given run of the machine, with virtually instantaneous switching between the standards made possible by the book selector 94. The entire system is readily adaptable to complete remote control, and it will be recognized that a computer or other program control can be employed to actuate the book selector 94 for widely varying book assembly programs. On the other hand, the system of the present invention does not require the use ofy a beta particle beam or other hard radiation apparatus.

We claim:

1. A caliper system for a cyclically operable signature gathering machine of the kind in which signatures are gathered from a plurality of supply sources into individual unbound books each containing a given number of signatures, and in which the unbound books are advanced seriatim along a predetermined path through a calipering station to a binding station comprising binding means for binding the books in their sequence of arrival, a-nd having control means for controlling operation of the machine, said caliper system comprising:

reference means for developing an alternating current electrical analog signal having a given parameter representative of the correct thickness for an unbound book; a fixed support located at said caliper station, on one 5 side of said path;

a probe element mounted at said caliper station, on the opposite side of said path and in alignment with said fixed support, said probe element being movable toward and away from said fixed support;

biasing means urging said probe element toward said fixed support so that, when an unbound book traverses said path through said caliper station, said probe element is displaced from said fixed support, by the unbound book, through a distance equal to the thickness of the unbound book;

an electrical transducer, connected to said probe element, for developing an alternating current book thickness signal, the corresponding parameter of which varies in accordance with the actual thickness of the unbound book;

means for comparing said analog signal and said book thickness signal to determine whether a match or a mismatch prevails and for developing a control signal indicative thereof;

and means for applying the control signal to the machine control means to inhibit binding of a mismatched book.

2. A caliper system for a signature gathering machine according to claim 1 in which said parameter of each of said signals is the signal amplitude.

3. A caliper system for a signature gathering machine according to claim 1 in which said electrical transducer comprises a transformer including at least an input windr ing and an output winding and a 'movable core for vary- 30 mg the coupling between said windings, said movable core being mechanically connected to said probe element.

l4. A caliper system for a signature gathering machine according to claim 1 in which said fixed support includes a roller mounted in fixed position at said caliper station on said one side of said path and said probe element comprises a roller movably mounted on the opposite side of said path.

5. A caliper system for a signature gathering machine according to claim 1 in which said reference means cornprises a reference fixed support for supporting a correctly assembled book employed as a standard book of correct thickness, a reference probe element movable toward and away from the reference support, biasing means urging the reference probe element toward the reference support so that the reference probe element is displaced from the reference support by the thickness of the standard book, and a reference electrical transducer, connected to said reference probe element, for developing said elecr-trical analog signal. 6. A caliper system for a signature gathering machine according to claim 5 in which each of the two transducers is a linear vvoltage differential transformer having a movable element mechanically connected to the probe element with which that transducer is associated.

7. A caliper system for a signature gathering machine according to claim 1 in which said reference means includes a plurality of individual means for developing a corresponding plurality of separate and individual analog signals each corresponding to a correctly assembled unbound book of a thickness different from the others, said system further comprising selective switching means for selecting any one of the analog signals for use in the system at any given time.

8. A caliper system for a signature gathering machine according to claim 7 in which the individual analog signal generating means each comprises a probe element engaging a correctly assembled book and an electrical transducer having a variable element mechanically connected to said sensing element.

9. A caliper system for a signature gathering machine according to claim 8 in which each transducer comprises a linear voltage differential transformer.

10. A caliper system for a signature gathering machine according to claim 1, and further comprising synchronizing means for delaying application of said control signal to said binder for a given number of machine cycles to synchronize inhibition of said binding means with the scheduled arrival of a mismatched book at said binding station.

11. A caliper system for a signature gathering machine according to claim 10 in which said synchronizing means comprises a multiple level storage register, each level of the storage register corresponding to an individual sequential stage in the advancing movement of the unbound books along said path from said calipering station to said binding station, and means for applying shift signals to said shift register in synchronism with the stage-bystage advancement of said unbound books along said path.

12. A caliper system for a signature gathering machine according to claim 11, in which the machine includes a transfer station for diverting mismatched books from said path to a different destination than the destination for matched books, and in which said machine control means 25 includes a transfer control and a binding means control, said system further including means for applying said control signal to said transfer control from one lelvel of said storage register and means for applying said control 12 signal to said binding means control from a different level of said storage register.

13. A caliper system for a signature gathering machine according to claim 11 in which said reference means includes a plurality of individual means for developing a corresponding plurality of separate and individual analog signals each corresponding to a correctly assembled unbound book of a constituency different than the others, said system further comprising selective switching means for selecting any one of the energy analogs for use in the system at any given time, said selective switching means being coupled to said signature supply sources to correlate the reference means and the signature contents of said unbound books.

References Cited UNITED STATES PATENTS 2,273,049 2/1942 Kieinberg 27o-56 3,191,925 6/1965 McCain et a1. 27d-56 3,561,752 2/1971 McCain et a1. 270-56 FOREIGN PATENTS 1,092,488 11/1960 Germany 27o-56 LAWRENCE CHARLES, Primary Examiner U.S. C1. X.R. 270-53, 54 

